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Guides

Developer guides — regex, encoding, HTTP, crypto

Short, practical explanations of things you hit daily: regex quirks, UUID versions, cron syntax, timestamps, JWT, character encoding, IP math. Each guide is paired with the AllYouNeed tool that applies it in the browser.

Fundamentals

UUID v4 vs v7 — When Timestamp-Ordered IDs Actually Matter
UUID v7 adds a millisecond timestamp prefix to random bytes. Here is when that matters for Postgres, MySQL, and distributed systems, and when v4 is still fine.
April 17, 2026

Encoding

Base64 in Production — When It Helps and When It Hurts
Base64 is a transport encoding, not compression and not encryption. When it earns its 33% overhead in real systems, and when it is a code smell to rip out.
April 17, 2026
Character Encoding for Developers — ASCII, UTF-8, UTF-16
Character encoding confuses people decades after it should be solved. Here is the mental model: code points, encodings, BOMs, and why UTF-8 almost always wins.
April 17, 2026
URL Encoding Rules — encodeURI vs encodeURIComponent and When Each Matters
URL encoding is simple until you build a URL from untrusted input. The rules behind percent-encoding, the two JavaScript functions, and the edge cases to actually care about.
April 17, 2026

Dates & Time

Cron Syntax — A Complete Practical Guide
Cron expressions explained: 5 fields, operators, aliases, the day-of-month vs day-of-week OR-logic trap, and the patterns that cover 95% of real jobs.
April 17, 2026
Timezone Handling for Backend Developers — Store UTC, Render Local
Timezones are where junior-senior experience shows up. The full discipline: store UTC, render local, handle DST, and the database column types that prevent silent corruption.
April 17, 2026
Unix Timestamps — Seconds, Milliseconds, Year 2038, and What to Watch For
Unix timestamps look simple and break in surprising ways. Seconds vs milliseconds, the 2038 problem, and the rules that keep time math from eating your app.
April 17, 2026

Regex

Regex Lookbehind Assertions Explained
Lookbehind lets you match something that is preceded by a pattern without consuming it. Here is how it works across JavaScript, Python, Go, PCRE, and when to actually use it.
April 17, 2026

Hashing & Crypto

Hash Functions Compared — MD5, SHA family, bcrypt, Argon2
Not all hash functions do the same job. When MD5 is still fine, why SHA-256 is the default, and why you must never hash passwords with either.
April 17, 2026

Networking

IP Addresses, CIDR, and Subnetting Basics You Can't Skip
CIDR, private ranges, and subnetting math without the networking jargon. The foundation every backend engineer should have for firewalls, VPCs, and routing.
April 17, 2026

Web & HTTP

JWT in 2026 — What Changed and What to Use Instead
JWT is still everywhere but its edges are sharper than most teams realize. Algorithm choices, revocation tradeoffs, and when opaque session tokens beat JWTs outright.
April 17, 2026

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